how to get the checkbox value from the LongListSelector in wp8 - windows-phone-8

Question

My Longlistselector DataTemplate
<DataTemplate x:Key="NotesListBoxItemTemplate">
<Grid HorizontalAlignment="Stretch">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*"/>
<ColumnDefinition Width="3*"/>
</Grid.ColumnDefinitions>
<CheckBox
Grid.Column="0" Grid.Row="0" Grid.RowSpan="2"
x:Name="chkDelete"
Visibility="Visible" Tap="chkDelete_Tap" Margin="0,36,0,0" />
<TextBlock
Text="{Binding NoteName}"
FontSize="{StaticResource PhoneFontSizeLarge}"
FontFamily="Segoe WP"
Grid.Row="0" Grid.Column="1" Margin="12,24,0,0" />
</Grid>
</DataTemplate>
and my Longlist selector is
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<ScrollViewer>
<phone:LongListSelector
x:Name="MainListBox"
ItemsSource="{Binding AllData}"
Margin="12, 0, 12, 0"
ItemTemplate="{StaticResource ListBoxItemTemplate}" />
</ScrollViewer>
</Grid>
How do I loop through the items and get the Checkbox checked state in each item? Previously I used ListBox and its worked correctly. And I am able to find out the checkbox value of the each item using below code
private T FindFirstElementInVisaulTree<T>(DependencyObject parentElement) where T:DependencyObject
ListBoxItem passed as a DependencyObject. The only problem with ListBox is scrolling. So trying for LongListSelector.
Please how do i loop through the items in LongListSelector.
Thank you

Answer 1

You can also Data Bind the state of the checkbox to your Model. Then you can just loop through the MainListBox.ItemsSource. If you do it this way you need to set the Binding Mode=Two Way or the collection will not change once someone taps the Checkbox. I would also recommend you use a Command to handle the Tap event on the Checkbox so you can handle in your ViewModel rather then Code behind. Here's my quick example modified from previous solutions I have posted:
// Namespaces used
using System.Collections.ObjectModel; // ObservableCollection<T>
using System.ComponentModel; // INotifyPropertyChanged
// sample_data class
public class sample_data : INotifyPropertyChanged
{
// simple constructor
public sample_data(string noteName, Boolean checkboxState)
{
this.NoteName = noteName;
this.CheckboxState = checkboxState;
}
// implement the INotify
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
// {Binding Properties}
Boolean checkbox_state;
public Boolean CheckboxState
{
get { return checkbox_state; }
set { checkbox_state = value; NotifyPropertyChanged("CheckboxState"); }
}
string note_name;
public string NoteName
{
get { return note_name; }
set { note_name = value; NotifyPropertyChanged("NoteName"); }
}
}
// create a sample set of data to show
private ObservableCollection<sample_data> CreateData()
{
ObservableCollection<sample_data> my_list = new ObservableCollection<sample_data>();
my_list.Add(new sample_data("one", false));
my_list.Add(new sample_data("two", true));
my_list.Add(new sample_data("three", false));
my_list.Add(new sample_data("four", true));
my_list.Add(new sample_data("five", false));
my_list.Add(new sample_data("six", true));
my_list.Add(new sample_data("seven", false));
my_list.Add(new sample_data("eight", true));
return my_list;
}
public MainPage()
{
InitializeComponent();
MainListBox.ItemsSource = CreateData(); // set the data bind
}
/// You can loop through the items like this, use any convention you want.
private void LoopThroughItems()
{
foreach (sample_data sd in MainListBox.ItemsSource)
{
Boolean is_check = sd.CheckboxState;
}
}
Your DataTemplate needs to change so it Databinds the checkbox with two-way binding.
<DataTemplate x:Key="NotesListBoxItemTemplate">
<Grid HorizontalAlignment="Stretch">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*"/>
<ColumnDefinition Width="3*"/>
</Grid.ColumnDefinitions>
<CheckBox Grid.Column="0" IsChecked="{Binding CheckboxState, Mode=TwoWay}" Grid.Row="0" Grid.RowSpan="2" x:Name="chkDelete" Visibility="Visible" Margin="0,36,0,0" />
<TextBlock Text="{Binding NoteName}" FontSize="{StaticResource PhoneFontSizeLarge}" FontFamily="Segoe WP" Grid.Row="0" Grid.Column="1" Margin="12,24,0,0" />
</Grid>
</DataTemplate>